Alkaline diet

The alkaline diet (also known as the alkaline ash diet, alkaline acid diet, acid ash diet, and the acid alkaline diet) is a diet based on the belief that certain foods, when consumed, leave an alkaline residue, or ash, in the body. Elements such as calcium, iron, magnesium, zinc, and copper are said to be the principal components of this "ash". Alkaline-diet proponents thus classify foods as alkaline, acid or neutral according to the pH of the solution created with its ash in water.

Alkaline diets are promoted and marketed primarily by practitioners of alternative medicine, with the claim that such diets might prevent cancer, fatigue, obesity, allergies, osteoporosis, and a variety of other physical complaints and illnesses. Proponents of an alkaline diet include Robert O. Young, Edgar Cayce, D. C. Jarvis, and Herman Aihara. A similar diet, called the Hay diet, was developed by the American physician William Howard Hay in the 1920s. A related alternative medical system called nutripathy was derived by another American, Gary A. Martin, in the 1970s.

There is no convincing scientific or medical evidence that an alkaline diet is beneficial to humans, nor that such diets prevent cancer, bone loss, or other maladies.

Diet composition

In general, the alkaline diet involves eating certain fresh citrus and other low-sugar fruits, vegetables, tubers, nuts, and legumes. The diet recommends avoiding grains, dairy, meat, sugar, alcohol, caffeine, and fungi. Proponents believe that such a diet maintains the balance of the slight alkalinity of blood without stressing the body's acid-base homeostasis.

Scientific evaluation

A selectively alkaline diet has not been shown to elicit a sustained change in blood pH levels, nor to provide the clinical benefits alleged by its proponents. Because of the body's natural regulatory mechanisms, eating an alkaline diet can, at most, change the blood pH minimally and transiently. In addition, the mechanisms by which an alkaline diet would produce the alleged benefits are vague, unknown, or nonfactual.

Recent systematic reviews of the published medical literature have found no indication that an alkaline diet can prevent osteoporosis, nor that such diets produce any beneficial effect on bone health whatsoever. Indeed, there is evidence that a diet rich calcium but not enriched with vitamin D may actually leach calcium from bones. As a result, alkaline diets are not widely accepted by the mainstream medical or scientific communities, and their promotion is sometimes described as pseudoscience. Alkaline diets are described as "nonsense" on the alternative-medicine watchdog site Quackwatch.